The present invention relates generally to fuel injector systems and, more particularly, to an electronically-controlled fuel injector.
Electronically-controlled fuel injectors are designed to inject precise amounts of fuel into an engine combustion chamber for combustion to generate motive power. The fuel injectors are connected to a fuel tank and include internal fluid chambers, fluid passages, and control valves that communicate fuel through the injector between injection events. During an injection sequence, the control valves move in a predetermined timing sequence to open and close the various fluid passages and fluid chambers so that pressurized fuel is injected into the combustion chamber at the appropriate time from an injection tip of the injector.
In prior fuel injectors, control valves within the injector have been actuated by one or more solenoids that receive control signals from an electronic control. In response to the control signals, the solenoids are operable to cause the control valves to move from one position to another so that fuel is communicated through the injector and to the injector tip in a desired manner. Compression springs may be used to move the control valves to a return position when the control signals are terminated.
In such solenoid-controlled injectors, it is often difficult to accurately control movement and positioning of the control valves through the control signals applied to the solenoids. This is especially true when intermediate positioning of a solenoid-controlled valve between two opposite, fixed positions is desired. Solenoid-controlled valves, by their very nature, are susceptible to variability in their operation due to inductive delays, eddy currents, spring pre-loads, solenoid force characteristics and varying fluid flow forces. Each of these factors must be considered and accounted for in a solenoid-controlled fuel injector design. Moreover, the response time of solenoids limits the minimum possible dwell times between multiple injection events and makes the fuel injector generally more susceptible to various sources of variability.
The present invention is directed to one or more of the problems set forth above.
While the invention is described in connection with certain embodiments, it will be understood that the invention is not limited to these embodiments. On the contrary, the invention includes all alternatives, modifications and equivalents as may be included within the spirit and scope of the present invention.
In one aspect, a fuel injector includes a spill control valve member and a needle control valve member at least partially positioned in an injector housing. A first electroactive bender actuator is operably coupled to move the spill control valve member. A second electroactive bender actuator is operably coupled to move the needle control valve member.
In another aspect, a method of injecting fuel includes a step of closing a spill valve at least in part by changing a voltage applied to a first electroactive bender actuator. A nozzle outlet is opened at least in part by changing a voltage applied to a second electroactive bender actuator.